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package org.openjdk.jmh.samples;


import org.openjdk.jmh.annotations.Benchmark;

import org.openjdk.jmh.annotations.BenchmarkMode;

import org.openjdk.jmh.annotations.Fork;

import org.openjdk.jmh.annotations.Measurement;

import org.openjdk.jmh.annotations.Mode;

import org.openjdk.jmh.annotations.OutputTimeUnit;

import org.openjdk.jmh.annotations.Scope;

import org.openjdk.jmh.annotations.Setup;

import org.openjdk.jmh.annotations.State;

import org.openjdk.jmh.annotations.TearDown;

import org.openjdk.jmh.annotations.Warmup;

import org.openjdk.jmh.runner.Runner;

import org.openjdk.jmh.runner.RunnerException;

import org.openjdk.jmh.runner.options.Options;

import org.openjdk.jmh.runner.options.OptionsBuilder;


import java.util.ArrayList;

import java.util.LinkedList;

import java.util.List;

import java.util.Queue;

import java.util.concurrent.TimeUnit;


@BenchmarkMode(Mode.AverageTime)

@OutputTimeUnit(TimeUnit.NANOSECONDS)

@Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)

@Measurement(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)

@Fork(1)

@State(Scope.Thread)

public class JMHSample_29_StatesDAG {


 /**

  * WARNING:

  * THIS IS AN EXPERIMENTAL FEATURE, BE READY FOR IT BECOME REMOVED WITHOUT NOTICE!

  */


 /**

  * There are weird cases when the benchmark state is more cleanly described

  * by the set of @States, and those @States reference each other. JMH allows

  * linking @States in directed acyclic graphs (DAGs) by referencing @States

  * in helper method signatures. (Note that {@link org.openjdk.jmh.samples.JMHSample_28_BlackholeHelpers}

  * is just a special case of that.

  *

  * Following the interface for @Benchmark calls, all @Setups for

  * referenced @State-s are fired before it becomes accessible to current @State.

  * Similarly, no @TearDown methods are fired for referenced @State before

  * current @State is done with it.

  */


 /*

  * This is a model case, and it might not be a good benchmark.

  * // TODO: Replace it with the benchmark which does something useful.

  */


 public static class Counter {

  int x;


  public int inc() {

   return x++;

  }


  public void dispose() {

   // pretend this is something really useful

  }

 }


 /*

  * Shared state maintains the set of Counters, and worker threads should

  * poll their own instances of Counter to work with. However, it should only

  * be done once, and therefore, Local state caches it after requesting the

  * counter from Shared state.

  */


 @State(Scope.Benchmark)

 public static class Shared {

  List<Counter> all;

  Queue<Counter> available;


  @Setup

  public synchronized void setup() {

   all = new ArrayList<>();

   for (int c = 0; c < 10; c++) {

    all.add(new Counter());

   }


   available = new LinkedList<>();

   available.addAll(all);

  }


  @TearDown

  public synchronized void tearDown() {

   for (Counter c : all) {

    c.dispose();

   }

  }


  public synchronized Counter getMine() {

   return available.poll();

  }

 }


 @State(Scope.Thread)

 public static class Local {

  Counter cnt;


  @Setup

  public void setup(Shared shared) {

   cnt = shared.getMine();

  }

 }


 @Benchmark

 public int test(Local local) {

  return local.cnt.inc();

 }


 /*

  * ============================== HOW TO RUN THIS TEST: ====================================

  *

  * You can run this test:

  *

  * a) Via the command line:

  *    $ mvn clean install

  *    $ java -jar target/benchmarks.jar JMHSample_29

  *

  * b) Via the Java API:

  *    (see the JMH homepage for possible caveats when running from IDE:

  *      http://openjdk.java.net/projects/code-tools/jmh/)

  */


 public static void main(String[] args) throws RunnerException {

  Options opt = new OptionsBuilder()

          .include(JMHSample_29_StatesDAG.class.getSimpleName())

          .build();


  new Runner(opt).run();

 }


// 本例展示了 @State 中嵌套 @State 的情况，不过想不出为啥需要这样做，例子中也说这是个实验性质的Feature。
}